Systems and methods for frequency equalization and temperature compensation in radio frequency devices

ABSTRACT

A frequency equalizer is provided. The frequency equalizer includes a coupler including a main segment extending between a first port and a second port and a coupled segment disposed in a coupling relationship with the main segment and extending between a third port and a fourth port. The frequency equalizer further includes a first thermistor electrically coupled in series between the first port and an input line, a second thermistor electrically coupled in series between the second port and an output line, and a first shunt resistor coupled across the third port. The frequency equalizer simultaneously provides frequency equalization and temperature compensation for signals transmitted through the frequency equalizer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/936,720 filed on Nov. 18, 2019, the disclosure of which is herebyincorporated by reference herein in its entirety as part of the presentapplication.

BACKGROUND

The embodiments described herein relate generally to radio frequency(RF) interconnects, and more particularly, to frequency equalization andtemperature compensation in RF devices.

RF devices are used for many applications, such as remote communicationand sensing. The performance of such devices, for example, the abilityof such devices to produce a desired output signal for a given inputsignal, may be affected by many different factors, such as a frequencyof the input signal and a temperature of the RF device. For example,attenuation of RF signals generally increases as the frequency of the RFsignal is increased. Further, as temperature increases, the attenuationof the RF signal generally increases correspondingly. Because RF devicesare generally required to perform relatively consistently over aspecified frequency range and/or temperature range, these interactionsmay be undesirable. However, the addition of compensation circuitry mayincrease costs of parts, manufacturing, and installation of the RFdevice, and once installed, may take up additional physical space withinthe RF application. A circuit that provides improved frequencyequalization and temperature compensation is therefore desirable.

BRIEF SUMMARY

In one aspect, a frequency equalizer is provided. The frequencyequalizer includes a coupler including a main segment extending betweena first port and a second port and a coupled segment disposed in acoupling relationship with the main segment and extending between athird port and a fourth port. The frequency equalizer further includes afirst thermistor electrically coupled in series between the first portand an input line, a second thermistor electrically coupled in seriesbetween the second port and an output line, and a first shunt resistorcoupled across the third port. The frequency equalizer simultaneouslyprovides frequency equalization and temperature compensation for signalstransmitted through the frequency equalizer.

In another aspect, an electronics package for a frequency equalizer isprovided. The electronics package includes a substrate having a firstsurface and a second surface, a ground plane disposed on the secondsurface, and a coupler including a main segment defined by a main stripdisposed on the first surface and by the ground plane. The main segmentextends between a first port and a second port. The coupler furtherincludes a coupled segment defined by a coupled strip disposed on thesecond surface and by the ground plane. The coupled segment is disposedin a coupling relationship with the main segment and extends between athird port and a fourth port. The electronics package further includes afirst thermistor disposed on the first surface and electrically coupledin series between the first port and an input line, a second thermistordisposed on the first surface and electrically coupled in series betweenthe second port and an output line, and a first shunt resistor disposedon the first surface and electrically coupled across the third port. Theelectronics package simultaneously provides frequency equalization andtemperature compensation for signals transmitted through the electronicspackage.

In another aspect, a method of manufacturing a frequency equalizer isprovided. The method includes forming a coupler including a main segmentextending between a first port and a second port and a coupled segmentdisposed in a coupling relationship with the main segment and extendingbetween a third port and a fourth port, electrically coupling a firstthermistor in series between the first port and an input line,electrically coupling a second thermistor in series between the secondport and an output line, and electrically coupling a first shuntresistor across the third port. The frequency equalizer simultaneouslyprovides frequency equalization and temperature compensation for signalstransmitted through the frequency equalizer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5 show exemplary embodiments of the systems and methodsdescribed herein.

FIG. 1 is a schematic diagram of an exemplary frequency equalizer;

FIG. 2 is a plan view of an exemplary electronics package that may be animplementation of the frequency equalizer shown in FIG. 1 ;

FIG. 3 is a plan view of another exemplary electronics package that maybe an implementation of the frequency equalizer shown in FIG. 1 ;

FIG. 4 is a plan view of another exemplary electronics package that maybe an implementation of the frequency equalizer shown in FIG. 1 ; and

FIG. 5 is a flowchart of an exemplary method of manufacturing afrequency equalizer as shown in FIG. 1 .

DETAILED DESCRIPTION

In the following specification and the claims, reference will be made toa number of terms, which shall be defined to have the followingmeanings.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

Approximating language, as used herein throughout the specification andclaims, is applied to modify any quantitative representation that couldpermissibly vary without resulting in a change in the basic function towhich it is related. Accordingly, a value modified by a term or terms,such as “about”, “approximately”, and “substantially”, are not to belimited to the precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. Here and throughout the specification andclaims, range limitations are combined and interchanged, such ranges areidentified and include all the sub-ranges contained therein unlesscontext or language indicates otherwise.

The systems and methods described herein facilitate combined frequencyequalization and temperature compensation for radio frequency (RF)applications using a single frequency equalizer circuit. The frequencyequalizer circuit utilizes a combination of couplers and thermistors toperform both frequency equalization and temperature compensation.Accordingly, the frequency equalizer, as described herein, enablesimproved frequency equalization and temperature compensation in an RFapplication, and reduces the amount of material and physical spaceneeded to perform frequency equalization and temperature compensation.

The subject matter described herein includes a frequency equalizer. Thefrequency equalizer includes a coupler that includes a main segmentextending between a first port and a second port and a coupled segmentdisposed in a coupling relationship with the main segment and extendingbetween a third port and a fourth port. The frequency equalizer furtherincludes a first thermistor electrically coupled in series between thefirst port and an input line; a second thermistor electrically coupledin series between the second port and an output line, and a first shuntresistor coupled across the third port. The frequency equalizersimultaneously provides frequency equalization and temperaturecompensation for signals transmitted through the frequency equalizer.

In some implementations, the frequency equalizer further includes asecond shunt resistor coupled across the fourth port.

In some implementations, the main segment and the coupled segment havedifferent widths.

In some implementations, the coupler further includes a second coupledsegment disposed in a second coupling relationship with the main segmentand extending between a fifth port and a sixth port, and the frequencyequalizer further includes a third shunt resistor and electricallycoupled across the fifth port and a fourth shunt resistor andelectrically coupled across the sixth port.

In some implementations, the coupler further includes a shunt lineextending between the main segment and the coupled segment.

In some implementations, a length of the main segment is greater than aquarter wavelength of an input signal for the frequency equalizer.

In some implementations, the frequency equalizer further includes afirst inductor electrically coupled in parallel with the firstthermistor and a second inductor electrically coupled in parallel withthe second thermistor.

In some implementations, at least one of the first thermistor and thesecond thermistor includes a thermistor paste.

In some implementations, the frequency equalizer further includes atleast one impedance tuning structure electrically coupled across atleast one of the input line, the output line, the first port, and thesecond port.

Referring now to FIG. 1 , a frequency equalizer 100 is shown. Frequencyequalizer 100 includes a coupler 102, a first thermistor 104, a secondthermistor 106, a first shunt resistor 108, a second shunt resistor 110,a first inductor 112, and a second inductor 114.

Coupler 102 includes a main segment 116 and a coupled segment 118. Mainsegment 116 is a transmission line segment extending between a firstport 120 and a second port 122. Coupled segment 118 is a transmissionline segment extending between a third port 124 and a fourth port 126.In some embodiments, main segment 116 and coupled segment 118 areimplemented as microstrip, stripline, and/or another type of RFtransmission line. Third port 124 is terminated with first shuntresistor 108, and fourth port 126 is terminated with second shuntresistor 110. In some embodiments, first shunt resistor 108 and secondshunt resistor 110 have a resistance selected to be a matched impedanceload for coupled segment 118. For example, in some embodiments, firstshunt resistor 108 and second shunt resistor 110 each have a resistanceof 50 ohms.

Coupled segment 118 is disposed in a coupling relationship with mainsegment 116. When RF power is received at first port 120, power istransmitted via second port 122 and fourth port 126. The amount of powertransmitted at one of second port 122 and fourth port 126 depends on thefrequency of the RF power received at first port 120. For example, whenthe input signal has a frequency (sometimes referred to herein as a“center frequency”) that corresponds to main segment 116 being onequarter wavelength, a maximum amount of RF power may be transferred tocoupled segment 118 and transmitted via fourth port 126, and a minimumamount of power may be transmitted via second port 122. As the frequencyof the input signal is increased above the center frequency, the amountof RF power transmitted via second port 122 increases. Accordingly, ifcoupler 102 is operated in a range greater than the center frequency,coupler 102 acts as an attenuator where the attenuation is inverselyproportional to input frequency, and coupled segment 118 compensates forthe tendency of RF signals to experience greater attenuation atincreasingly higher frequencies.

In some embodiments, main segment 116 and coupled segment 118 havecertain transmission line characteristics (e.g., characteristicimpedance, electrical length, distance between transmission lines, etc.)selected to achieve a particular relationship between frequency andattenuation. For example, in some embodiments, main segment 116 andcoupled segment 118 are microstrip lines each having a different widthand/or shape that is selected to achieve a particular couplingrelationship.

First thermistor 104 is electrically coupled between first port 120 ofcoupler 102 and an input 128, and second thermistor 106 is electricallycoupled between second port 122 of coupler 102 and an output 130. Insome embodiments, input 128 and output 130 are, for example, an inputtransmission line and an output transmission line, wherein frequencyequalizer 100 receives an input signal at input 128 and transmits anoutput signal at output 130. First thermistor 104 and second thermistor106 have a resistance that changes in response to a change intemperature of respective first thermistor 104 or second thermistor 106.For example, in some embodiments, first thermistor 104 and secondthermistor 106 are negative temperature coefficient (NTC) thermistorsthat have a resistance that decreases as temperature increases.Accordingly, the attenuation of the input signal by first thermistor 104and second thermistor 106 decreases as temperature increases, such thatfrequency equalizer 100 compensates for the tendency of RF signals toexperience greater attenuation at increasing temperatures.

First inductor 112 is electrically coupled in parallel with firstthermistor 104, and second inductor 114 is electrically coupled inparallel with second thermistor 106. First inductor 112 and secondinductor 114 have each have an inductance that, at a predeterminedoperating frequency, tunes out a parasitic capacitance at firstthermistor 104 and second thermistor 106, respectively.

FIG. 2 is a plan view of an exemplary electronics package 200.Electronics package 200 is an exemplary implementation of frequencyequalizer 100 (shown in FIG. 1 ). Electronics package 200 includes asubstrate 202. Electronics package 200 further includes coupler 102,first thermistor 104, second thermistor 106, first shunt resistor 108,second shunt resistor 110, first inductor 112, and second inductor 114,which are implemented as microstrip disposed on a front side ofsubstrate 202 and generally function as described with respect to FIG. 1. Electronics package 200 additionally includes impedance tuningstructures 204, which are also implemented as microstrip disposed on thefront side of substrate 202. Electronics package 200 further includes aground plane (not shown) disposed on a reverse side of substrate 202.

Electronics package 200 includes conductive traces (e.g., microstrip)that, together with the ground plane, define, for example, main segment116, coupled segment 118, first thermistor 104, second thermistor 106,first shunt resistor 108, second shunt resistor 110, first inductor 112,and second inductor 114. In some embodiments, at least one of firstthermistor 104, second thermistor 106, first shunt resistor 108, andsecond shunt resistor 110 include a paste (e.g., a thermistor paste)disposed on substrate 202. Additionally or alternatively, in someembodiments, at least one of first thermistor 104, second thermistor106, first shunt resistor 108, and second shunt resistor 110 includeother types of resistive components (e.g., surface mount technology(SMT) components).

Impedance tuning structures 204 are coupled across input 128, output130, first port 120, and second port 122. Impedance tuning structures204 include microstrip disposed on the front surface of substrate 202and a through hole 206 extending between and forming an electricalconnection between the microstrip and the ground plane disposed on theback surface of substrate 202. In some embodiments, impedance tuningstructures 204 have, for example, a length that is selected to tune outa parasitic capacitance in electronics package 200 at the predeterminedoperating frequency.

FIG. 3 is a plan view of another exemplary electronics package 300.Electronics package 300 is another exemplary implementation of frequencyequalizer 100 (shown in FIG. 1 ). Electronics package 300 includescoupler 102, first thermistor 104, second thermistor 106, first shuntresistor 108, second shunt resistor 110, first inductor 112, secondinductor 114, substrate 202, impedance tuning structures 204, andthrough holes 206, which generally operate as described with respect toFIGS. 1 and 2 . Electronics package 300 further includes a secondcoupled segment 302, a third shunt resistor 304, and a fourth shuntresistor 306.

Second coupled segment 302 extends between a fifth port 308 and a sixthport 310. Fifth port 308 is terminated with third shunt resistor 304,and sixth port 310 is terminated with fourth shunt resistor 306. Thirdshunt resistor 304 and fourth shunt resistor 306 are matched impedanceloads for second coupled segment 302. For example, in some embodiments,third shunt resistor 304 and fourth shunt resistor 306 each have aresistance of 50 ohms.

Second coupled segment 302 is disposed in a coupling relationship withmain segment 116. Second coupled segment 302 generally functions asdescribed with respect to coupled segment 118 (shown in FIG. 1 ), and,together with coupled segment 118, serves to compensate for the tendencyof RF signals to experience greater attenuation at increasingly higherfrequencies. Second coupled segment 302 further increases coupling(e.g., a transfer of RF power away from main segment 116). Accordingly,electronics package 300 has an enhanced ability to achieve a particulardesired relationship between frequency and attenuation.

FIG. 4 is a plan view of another exemplary electronics package 400.Electronics package 400 is another exemplary implementation of frequencyequalizer 100 (shown in FIG. 1 ). Electronics package 400 includescoupler 102, first thermistor 104, second thermistor 106, first shuntresistor 108, first inductor 112, second inductor 114, substrate 202,impedance tuning structures 204, through holes 206, second coupledsegment 302, and third shunt resistor 304, which generally operate asdescribed with respect to FIGS. 1-3 . FIG. 4 further includes a firstshunt line 402 and a second shunt line 404.

First shunt line 402 is a microstrip line extending between first port120 and fourth port 126, and second shunt line 404 is a microstrip lineextending between first port 120 and sixth port 310. First shunt line402 and second shunt line 404 further increase coupling (e.g., atransfer of RF power away from main segment 116). Accordingly,electronics package 400 has an enhanced ability to achieve a particulardesired relationship between frequency and attenuation.

FIG. 5 is an exemplary method 500 for manufacturing frequency equalizer100 (shown in FIG. 1 ). In the exemplary embodiment, method 500 includesforming 502 a coupler (e.g., coupler 102) including a main segment(e.g., main segment 116) extending between a first port (e.g., firstport 120) and a second port (e.g., second port 122) and a coupledsegment (e.g., coupled segment 118) disposed in a coupling relationshipwith the main segment and extending between a third port (e.g., thirdport 124) and a fourth port (e.g., fourth port 126). Method 500 furtherincludes electrically coupling 504 a first thermistor (e.g., firstthermistor 104) in series between the first port and an input line.Method 500 further includes electrically coupling 506 a secondthermistor (e.g., second thermistor 106) in series between the secondport and an output line. Method 500 further includes electricallycoupling 508 a first shunt resistor (e.g., first shunt resistor 108)across the third port, wherein frequency equalizer 100 simultaneouslyprovides frequency equalization and temperature compensation for signalstransmitted through frequency equalizer 100.

Exemplary embodiments of methods and systems are described above indetail. The methods and systems are not limited to the specificembodiments described herein, but rather, components of systems and/orsteps of the methods may be used independently and separately from othercomponents and/or steps described herein. Accordingly, the exemplaryembodiment can be implemented and used in connection with many otherapplications not specifically described herein.

Technical effects of the systems and methods described herein include atleast one of (a) providing frequency equalization for attenuation in anRF device using a coupler having a length greater than one quarterwavelength of the input signal; (b) providing temperature compensationfor attenuation in an RF device using one or more thermistors; and (c)reducing an amount of physical space of a frequency equalization andtemperature compensation circuit by integrating frequency equalizationand temperature compensation into a single electronics package.

Although specific features of various embodiments of the disclosure maybe shown in some drawings and not in others, this is for convenienceonly. In accordance with the principles of the disclosure, any featureof a drawing may be referenced and/or claimed in combination with anyfeature of any other drawing.

This written description uses examples to disclose various embodiments,including the best mode, and also to enable any person skilled in theart to practice the disclosure, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal language of the claims.

What is claimed is:
 1. A frequency equalizer comprising: a couplercomprising: a main segment extending between a first port and a secondport; and a coupled segment disposed in a coupling relationship withsaid main segment and extending between a third port and a fourth port;a first thermistor electrically coupled in series between the first portand an input line; a second thermistor electrically coupled in seriesbetween the second port and an output line; and a first shunt resistorcoupled across the third port, wherein said frequency equalizersimultaneously provides frequency equalization and temperaturecompensation for signals transmitted through said frequency equalizer.2. The frequency equalizer of claim 1, further comprising a second shuntresistor coupled across the fourth port.
 3. The frequency equalizer ofclaim 1, wherein said main segment and said coupled segment havedifferent widths.
 4. The frequency equalizer of claim 1, wherein saidcoupler further comprises a second coupled segment disposed in a secondcoupling relationship with the main segment and extending between afifth port and a sixth port, and wherein said frequency equalizerfurther comprises: a third shunt resistor and electrically coupledacross the fifth port; and a fourth shunt resistor and electricallycoupled across the sixth port.
 5. The frequency equalizer of claim 1,wherein said coupler further comprises a shunt line extending betweensaid main segment and said coupled segment.
 6. The frequency equalizerof claim 1, wherein a length of the main segment is greater than aquarter wavelength of an input signal for said frequency equalizer. 7.The frequency equalizer of claim 1, further comprising a first inductorelectrically coupled in parallel with said first thermistor and a secondinductor electrically coupled in parallel with said second thermistor.8. The frequency equalizer of claim 1, wherein at least one of saidfirst thermistor and said second thermistor comprises a thermistorpaste.
 9. The frequency equalizer of claim 1, further comprising atleast one impedance tuning structure electrically coupled across atleast one of the input line, the output line, the first port, and thesecond port.
 10. An electronics package for a frequency equalizercomprising: a substrate having a first surface and a second surface; aground plane disposed on the second surface; a coupler comprising: amain segment defined by a main strip disposed on the first surface andby said ground plane, said main segment extending between a first portand a second port; and a coupled segment defined by a coupled stripdisposed on the second surface and by said ground plane, said coupledsegment disposed in a coupling relationship with said main segment andextending between a third port and a fourth port; a first thermistordisposed on the first surface and electrically coupled in series betweenthe first port and an input line; a second thermistor disposed on thefirst surface and electrically coupled in series between the second portand an output line; and a first shunt resistor disposed on the firstsurface and electrically coupled across the third port, wherein saidelectronics package simultaneously provides frequency equalization andtemperature compensation for signals transmitted through saidelectronics package.
 11. The electronics package of claim 10, furthercomprising a second shunt resistor disposed on the first surface andelectrically coupled across the fourth port.
 12. The electronics packageof claim 10, wherein said main strip and said coupled strip havedifferent widths.
 13. The electronics package of claim 10, wherein saidcoupler further comprises a second coupled segment defined by a secondcoupled strip disposed on the first surface and by said ground plane,said second coupled segment disposed in a second coupling relationshipwith the main segment and extending between a fifth port and a sixthport, and wherein the frequency equalizer further comprises: a thirdshunt resistor disposed on the first surface and electrically coupledacross the fifth port; and a fourth shunt resistor disposed on the firstsurface and electrically coupled across the sixth port.
 14. Theelectronics package of claim 10, wherein said coupler further comprisesa shunt line extending between said main segment and said coupledsegment.
 15. The electronics package of claim 10, wherein a length ofthe main segment is greater than a quarter wavelength for an inputsignal of the frequency equalizer.
 16. The electronics package of claim10, further comprising a first inductor electrically coupled in parallelwith said first thermistor and a second inductor electrically coupled inparallel with said second thermistor.
 17. The electronics package ofclaim 10, wherein at least one of said first thermistor and said secondthermistor comprise a thermistor paste disposed on the first surface.18. The electronics package of claim 10, further comprising at least oneimpedance tuning structure electrically coupled across at least one ofthe input line or the output line.
 19. A method of manufacturing afrequency equalizer, said method comprising: forming a coupler includinga main segment extending between a first port and a second port and acoupled segment disposed in a coupling relationship with the mainsegment and extending between a third port and a fourth port;electrically coupling a first thermistor in series between the firstport and an input line; electrically coupling a second thermistor inseries between the second port and an output line; and electricallycoupling a first shunt resistor across the third port, wherein thefrequency equalizer simultaneously provides frequency equalization andtemperature compensation for signals transmitted through the frequencyequalizer.
 20. The method of claim 19, further comprising electricallycoupling a second shunt resistor across the fourth port.